Binocular

ABSTRACT

A binocular includes two telescope systems with parallel axes, eyepiece frames, adjustable eye cups, operation controls positioned between the telescope systems, a focus adjustment mechanism, a diopter correction mechanism, and a magnifying-power-varying mechanism. The focus adjustment mechanism and diopter correction mechanism are arranged coaxially. The magnifying-power-varying mechanism includes rotatable cam rings and guide rings connected by a single connecting belt that moves perpendicular to the optical axes to rotate the cam rings. The connecting belt is supported and held in position so that it does not bind. The position of magnifying-power-varying lenses can be adjusted. During assembly, the magnifying-power-varying lenses can be mounted in the guide rings in a number of positions by rotating the lens frames holding the lenses about the optical axis and inserting sliders in linear guide grooves. Further, after assembly, the position of the magnifying-power-varying lenses along the optical axes in relation to the guide rings and cam rings can be adjusted.

This application is a divisional of application Ser. No. 08/702,091,filed Aug. 23, 1996, the contents of which are herein incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a binocular.

A conventional binocular includes two telescope systems that haveparallel optical axes, an interpupillary adjustment mechanism, a focusadjustment mechanism, a magnifying-power-varying mechanism, and adiopter correction mechanism.

The conventional interpupillary adjustment mechanism is provided so thatthe left and right telescope systems are rotatable about a shaftprovided to the center of the left and right telescope systems.

Conventionally, the magnifying-power-varying mechanism includes a lensgroup designated as a magnifying-power-varying lens group provided inthe left and right telescope systems and operates to move themagnifying-power-varying lens groups along the optical axes thereof. Themagnifying-power-varying lens groups are moved by driving membersprovided in the left and right telescope systems.

Since the interaxial distance between the left and right telescopesystems is varied by the interpupillary adjustment, in order tosimultaneously vary the magnification power of both the left and righttelescope systems, the driving members are connected by a connectingmember, such as string. A magnifying-power-varying activator, forexample a knob, is provided on one of the telescope systems, usually onthe right telescope system, to allow the user to actuate the drivingmembers. The operation of the magnifying-power-varying activator movesthe right driving member, and the movement of the right driving memberis transmitted to the left driving member by the connecting member.

However, if the magnifying-power-varying activator is provided on theright viewer portion, it is inconvenient for a left-handed user. Abinocular should be easily operated by both right-handed and left-handedusers.

Further, in a conventional binocular the driving members and connectingmember are arranged in a complicated manner using pulleys or the like,which makes the assembly of the binocular complicated. Also, often thereis a difference between the axial position of the driving members andthe axial position of the connecting member, such that the connectingmember is not perpendicular with respect to the rotation axes of thedriving members. In such an arrangement, the connecting member may notmove smoothly and has a greater potential to bind or fail. Accordingly,a simple means of synchronizing the movement of both driving members andtherefore both magnifying-power-varying lenses is desirable.

Furthermore, conventionally, the position of themagnifying-power-varying lenses with respect to the rotation of thedriving members is not adjustable. Therefore, a binocular wherein theposition of the magnifying-power-varying lenses with respect to thedriving members can be adjusted is desirable.

Conventionally, the driving members for the magnifying-power-varyingmechanism are cam rings and guide rings. In such an arrangement, lensframes that support the magnifying-power-varying lenses include campins, and each cam pin is inserted through both a guide groove on theguide ring and a cam groove on the cam ring. If an excessive drivingforce is applied to the cam pins, the lens frames may break.Accordingly, a binocular must be designed to prevent the lens framesfrom breaking when an excessive force is applied to the cam pins.

Further, in a conventional binocular, it there is a difference betweenthe visual fields seen through the left and right telescope systems,because of a lens mounting error or the like, replacement of the faultylens is necessary. Accordingly, a binocular wherein the position of animproperly mounted lens can be adjusted to correct for a differencebetween the visual fields of the telescope systems is desirable.

A conventional binocular also has adjustable eye cups, which areslidable between a projected position and a retracted position. Aspectacle-wearing user can use the binocular with the eye cup retracted,allowing the spectacle lenses to be closer to the telescope systems. Theeye cups have a locking mechanism to keep them in position, generallyincluding two holes formed on the eye cup and one protrusion formed onthe viewer portion, such that the protrusion locks into one of the twoholes for each position. However, it too much force is applied to theeye cup this locking mechanism is unstable and the eye cup can beaccidentally moved from the extended position to the retracted position.

Conventionally, the end surface of an eyepiece frame that is facing theuser has a flat cross-section such that a further problem is that, ifthe user wears spectacles, the curvature of the spectacle lenses mayinterfere with the flat end surface of the eyepiece frame.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved binocular, and more specifically to provide a binocular that iseasily operated by both left-handed and right-handed users.

According to an aspect of the present invention, a binocular includes:

two telescope systems having parallel optical axes;

a focus adjusting mechanism for focusing the telescope systems;

a diopter correction mechanism for adjusting a diopter of the telescopesystems relative to each other;

a magnifying-power-varying mechanism for adjusting the magnifying-powerof the telescope systems; and

operation controllers for operating the focus adjusting mechanism, thediopter correction mechanism, and the magnifying-power-varyingmechanism. The operation controllers are centered between the twotelescope systems.

Since the operation controllers are centered, they are equallyaccessible to left-handed and right-handed users.

In a particular arrangement, the operation controllers are rotatableabout a coaxial rotation axis for driving the focus adjusting mechanism,the diopter correction mechanism, and the magnifying-power-varyingmechanism.

Preferably, the rotation axis of the three operation controllers isparallel to the optical axes of the telescope systems in order to allowa more compact binocular design.

In this aspect, each of the telescope systems of the binocular includesa lens group designated as a magnifying-power-varying lens group, andthe magnifying-power-varying mechanism includes: drive members that arerotatable about the optical axes in order to move themagnifying-power-varying lens groups along the optical axes; and aconnecting member that synchronously rotates the drive members inresponse to activation of the magnifying-power-varying mechanism.

Preferably, the connecting member is a belt-shaped material having apredetermined rigidity, and the longitudinal ends of the connectingmember are fixed to the drive members so that when the connecting memberis driven perpendicular to the optical axes, the connecting memberpushes the outer surface of one of the drive members and pulls the outersurface of the other of the drive members thereby rotating both of thedrive members at the same time.

Advantageously, the magnifying-power-varying mechanism further includesrollers and guide members that support and guide the connecting member.

Using a single connecting member that is supported and guided by simpledevices decreases the chances of the connecting member binding andsimplifies assembly.

In particular, if each of the telescope systems includes an objectoptical system and an eyepiece optical system, and an object opticalaxis of a frontmost lens of the object lens system and an eyepieceoptical axis of the eyepiece optical system being parallel but notcoaxial, at least the eyepiece optical systems being rotatable about theobject optical axes for interpupillary adjustment, the rollers arepositioned to support the connecting member at the object optical axesduring the interpupillary adjustment so that themagnifying-power-varying mechanism is not affected by the interpupillaryadjustment.

In a further development of this aspect of the present invention:

the operation controllers are first, second and third operation knobs;

the focus adjustment mechanism includes a first actuator and a secondactuator which are parallel to the optical axes and which are drivenalong the optical axes by the first operation knob;

the diopter correcting mechanism shares the second actuator with thefocus adjustment mechanism such that rotation of the second operationknob only drives the second actuator;

and the magnifying-power-varying mechanism further includes a thirdactuator that is driven by the third operation knob to moveperpendicular to the optical axes and drive the connecting member.

In particular, when using the focus adjustment mechanism, the axialmovement of the first actuator moves the frontmost lens of the objectoptical system of a first telescope system, and the axial movement ofthe second actuator moves the frontmost lens of the object opticalsystem of a second telescope system along the optical axes. Further,when using the diopter correction mechanism, the second actuator isdriven to move the frontmost lens of the object optical system of asecond Telescope system with respect to the frontmost lens of the objectoptical system of a first telescope system.

In a particular arrangement, the third operation knob is providedbetween the first and second operation knobs, and the second actuator isinserted through the third operation knob into the first actuator.

Preferably, the second operation knob (for the diopter correctionmechanism) is storable into and extendable from at least one of thefirst and third operation knobs. Diopter correction is generallyperformed less frequently and thus the ability to store this operationknob makes the binocular more compact and lessens the chance that thediopter correction mechanism will be operated accidentally.

Also preferably, the focus adjusting mechanism includes a first arm andsecond arm that respectively engage lens frames holding the focusinglenses in the telescope systems. The first arm and the second arm areguided parallel to the optical axes by a guiding mechanism provided inthe binocular. Further, each of the first arm and the second arm includea hole which contains a biasing member, such as a spring, which comesinto contact with the lens frames to regulate their vertical position.

A binocular according to this aspect is compact and easy to assemble andincludes a simple magnifying-power-varying mechanism which is notaffected by interpupillary adjustment and in which there is littlechance of the connecting member binding during movement.

It is another object of the present invention to provide a binocularthat is compact.

According to another aspect of the present invention, the binocularincludes:

two telescope systems having parallel optical systems, each telescopesystem including a lens group designated as a magnifying-power-varyinglens group; and

a magnifying-power-varying mechanism for moving themagnifying-power-varying lens groups.

The magnifying-power-varying mechanism includes drive members in eachtelescope system and a connecting member that connects the drivemembers.

The drive members are rotatable around the optical axes to move themagnifying-power-varying lens groups along the optical axes.

The connecting member is made of a belt-shaped material having apredetermined rigidity, and its longitudinal ends are fixed to outersurfaces of the drive members. In this way, when the connecting memberis driven perpendicular to the optical axes, the connecting memberpushes the outer surface of one of the drive members and pulls the outersurface of the other of the drive members thereby to rotate both of thedrive members.

Preferably, the connecting member has an engaging portion at bothlongitudinal ends that engages with the drive members. In a particulararrangement, each of the engaging portions includes a bent portion atthe longitudinal end of the connecting member and a tongue portionformed at a predetermined distance from the bent portion. Further, thebent portion has a rounded corner to reduce the chances of theconnecting member binding during movement.

A particular connecting member is made of metal, for example, Ni--Cr--Moalloy.

A binocular according to this aspect includes a simplemagnifying-power-varying mechanism in which there is little chance ofthe connecting member binding.

Further, the magnifying-power-varying mechanism is further defined inthat the drive members have slits for engaging the bent portions and thetongue portions.

In particular, the tongue portions are formed as a rectangle cut andbent out from the connecting member. Further, the distance between eachbent portion and each tongue portion is less than the distance betweenthe slits on each drive member, so that the bent portion and the tongueportion clamp the connecting member to the drive members.

Preferably, to further secure the connecting member to the drivemembers, a predetermined length of the connecting member is wrappedaround each drive member.

For easier assembly, the slits of each drive member have openings, atone longitudinal end surface of the drive member, for inserting the bentportion and the tongue portion. Preferably, the slits have a flaredopening for inserting the bent portion and the tongue portion.

In yet a further development of this aspect, the drive members includedrive rings that are rotatably provided for axially moving themagnifying-power-varying lens groups, and the connecting member attachesto and synchronously rotates the drive rings. Further, a regulatingmember regulates the position of the connecting member in a directionparallel to the optical axes.

In a particular arrangement, the regulating member includes regulatingplates provided in front of the connecting member. Preferably, theregulating plate also contacts reference surfaces of the drive rings toregulate the drive rings in the same direction.

In this way, the drive rings are kept in position and the connectingmember is prevented from binding due to twisting away from it axis ofmovement (that is, perpendicular to the optical axes).

It is still another object of the present invention to provide abinocular that is easy to assemble.

According to still another aspect of the present invention, each of thetelescope systems includes an object optical system and an eyepieceoptical system, an object optical axis of a frontmost lens of the objectoptical system and an eyepiece optical axis of the eyepiece opticalsystem are parallel, but not coaxial. Further, the eyepiece opticalsystem of each telescope system is rotatable about the object opticalaxis for interpupillary adjustment.

In this aspect, for easier assembly, a first unit includes at leastfrontmost lenses of the object optical systems, and a second unitincludes at least eyepiece optical systems. Thus, each unit can beassembled separately and then be simply connected to each other.

Further, the first unit further includes erecting systems and the secondunit further includes the remaining lens groups of the object opticalsystems other than the frontmost lenses.

In a particular arrangement, each telescope system has amagnifying-power-varying lens group. The magnifying-power-varying lensgroup includes the remaining lens group of each object lens system otherthan the frontmost lens and lens group of the objective side of theeyepiece optical system.

Assembly is further simplified if, by assembling the second unit to thefirst unit, the position (along the optical axes) of the components ofthe second unit are determined by the positions of the components of thefirst unit.

It is yet another object of the present invention to provide a binocularin which the binding of a connecting member between driving members canbe prevented.

According to yet another aspect of the present invention, each of thetelescope systems includes an object optical system and an eyepieceoptical system, an object optical axis of a frontmost lens of the objectoptical system and an eyepiece optical axis of the eyepiece opticalsystem are parallel but not coaxial. Further, the eyepiece opticalsystems are rotatable about the object optical axes for interpupillaryadjustment. Each telescope system further includes a lens groupdesignated as a magnifying-power-varying lens group.

The magnifying-power-varying mechanism is for moving themagnifying-power-varying lens groups and includes drive members, aconnecting member and at least one regulating member.

The drive members include drive rings rotatably provided for axiallymoving the magnifying-power-varying lens groups. The connecting memberis belt-shaped and synchronously rotates the drive rings. The regulatingmember regulates the position of the connecting member within apredetermined range in a direction parallel to the optical axes.

In this aspect, for easier assembly, a first unit includes at least thefrontmost lens of the object optical systems and a second unit includesthe eyepiece optical systems.

The second unit further includes:

rear barrels for supporting remaining lens groups of the object opticalsystem other than the frontmost lenses and lens groups of objective sideof eyepiece optical systems;

a support frame for supporting the rear barrels with a predeterminedmargin for adjustment in the direction of the eyepiece optical axes; and

the magnifying-power-varying mechanism.

Since the second unit includes all the necessary elements for theassembly of the magnifying-power-varying mechanism with the telescopesystems, the second unit can be completely assembled independently ofthe first unit and then simply attached to the first unit.

As in other aspects of the invention, the connecting member has apredetermined rigidity and its longitudinal ends are fixed to the outersurfaces of the drive rings such that when the connecting member isdriven perpendicular to the optical axes, the connecting member pushesthe outer surface of one of the drive rings and pulls the outer surfaceof the other of the drive rings thereby rotating both of the drive ringsat the same time.

Further, the regulating member includes a regulating plate provided infront of the connecting member which also contacts a reference surfaceof each drive ring to thereby also regulate the positions of theconnecting member and the drive rings along the optical axes.

In a particular arrangement, the drive rings have portions about whichthe longitudinal ends of the connecting member are wrapped. Theseportions of the drive rings are larger in the optical axes directionthan the connecting member so that the position of the drive rings alongthe optical axes can be finely adjusted independently without dislodgingthe connecting member.

It is yet still another object of the present invention to provide abinocular in which the position of the driving members in relation tolens frames holding magnifying-power-varying lenses can be adjustedafter assembly.

According to yet still another aspect of the present invention, thebinocular includes:

two telescope systems having parallel optical axes, each telescopesystem further including a lens group designated as amagnifying-power-varying lens group and further including a barrel forsupporting the magnifying-power-varying lens group; and

a magnifying-power-varying mechanism for moving themagnifying-power-varying lens groups.

The magnifying-power-varying mechanism includes drive members and aconnecting member.

The drive members include guide rings for guiding themagnifying-power-varying lens groups along the optical axes and camrings rotatably provided for actuating the magnifying-power-varying lensgroups. In particular, the magnifying-power-varying mechanism isarranged such that the positions of the guide rings with respect to thetelescope systems can be adjusted.

For adjustment, the guide rings have operation members and the barrelshave openings to allow access to the operation members from the exteriorof the binocular. In a particular arrangement, the opening is covered byan eye cup to prevent the operation members from being movedaccidentally.

In order to facilitate the movement of the magnifying-power-varying lensgroups, the guide rings have linear guide grooves extending along theoptical axes and the cam rings have cam grooves.

In this aspect, the guide rings, and thus, the position of themagnifying-power-varying lens groups can be independently adjusted, evenafter assembly.

It is a further object of the present invention to provide a binocularin which the breaking of lens frames can be prevented if an excessiveforce is applied.

According to a further aspect of the present invention, the binocularincludes:

two telescope systems having parallel optical axes, each of thetelescope systems including a lens group designated as amagnifying-power-varying lens group and a lens frame for holding themagnifying-power-varying lens group; and

a magnifying-power-varying mechanism for moving themagnifying-power-varying lens groups.

The magnifying-power-varying mechanism includes drive members and aconnecting member.

The drive members include guide rings for guiding themagnifying-power-varying lens groups along the optical axes, and camrings rotatably provided for moving the magnifying-power-varying lensgroups.

In particular, the lens frames include sliders, for engaging linearguide grooves provided on the guide rings, and cam pins, for engagingcam grooves on the cam rings. Preferably, the cam pins are fixable tothe sliders. Also preferably, the cam rings are on the outside of theguide rings.

In a particular arrangement, the linear guide grooves are internalgrooves formed on the inner surfaces of the guide rings, and at leastone guide groove of each guide ring has a hole through which the cam pinprojects to engage the cam groove.

In this aspect, since the cam pins are fixed to the sliders (notdirectly to the circumference of the lens frames), and the sliders arein guide grooves, any excessive force that is applied to the cam pinswill be partially absorbed by the sliders preventing the lens frame frombreaking.

It is a still further object of the present invention to provide abinocular in which the difference in visual fields observed through theleft and right telescope systems can be compensated.

According to a still further aspect of the present invention, thebinocular includes:

two telescope systems having parallel optical axes, each of thetelescope systems including a lens group designated as amagnifying-power-varying lens group and a lens frame for holding themagnifying-power-varying lens group; and

a magnifying-power-varying mechanism for moving themagnifying-power-varying lens groups.

The magnifying-power-varying mechanism includes drive members and aconnecting member.

The drive members include guide rings for guiding themagnifying-power-varying lens groups along the optical axes in linearguide grooves.

In particular, each of the lens frames has at least one slider which canengage at least one of the linear guide grooves, and each of the guiderings has a plurality of guide grooves such that the lens frames can bemounted in the guide rings in a plurality of positions by rotating thelens frames about the optical axes.

Preferably, the linear guide grooves are provided at regular intervals,for example, 90 degree intervals, around the circumference of the guiderings and the sliders are provided at regular intervals.

In a particular arrangement, cam rings having cam grooves are providedto the periphery of the guide rings, cam pins are provided on thesliders, and at least one hole is formed on at least one guide groove ofeach guide ring. The cam pin projects through the hole to engage the camgroove.

In this arrangement, the cam pin can be provided to any slider of thelens frame, and the lens frames can be mounted to the guide rings in aplurality of positions by rotating around the optical axis, so that anymounting error of the lens in the lens frame can be compensated for.

It is yet still further object of the present invention to provide abinocular having lens frames that do not interfere with a user'sspectacle lenses.

According to a further development of any of the aspects above, thebinocular includes an eyepiece frame for holding a rearmost lens of theeyepiece optical system. The eyepiece frame is such that an end surfaceof the eyepiece frame that is facing the user is concave with apredetermined curvature. This predetermined curvature will prevent theeyepiece frame from interfering with a user's spectacles.

In a particular arrangement, the eyepiece frame has a threaded portionwhich can be engaged to a barrel of a telescope system of the binocular.With this construction, the eyepiece frame is easily assembled to thebinocular and can be easily removed for use with other binoculars oroptical devices.

The threading on the eyepiece frame also allows the eyepiece frame tosecure the axial position of a lens group of objective side of theeyepiece optical system.

It is another object of the present invention to provide a binocularthat has a stable locking mechanism for eye cups.

According to another development of any of the aspects above, thebinocular includes a locking mechanism for locking an eye cup to abarrel of the binocular.

In this locking mechanism, at least three indentations are formed on oneof an outer surface of the barrel and an inner surface of the eye cup,and two protrusions are formed on the other of the outer surface of thebarrel and the inner surface of the eye cup. In this way, the eye cupcan be secured in a predetermined position by the engagement of the twoprotrusions and two of the three indentations.

Preferably, the indentations are formed in a groove having the samewidth as the indentations, the groove regulating the position, in thecircumferential direction, of the eye cup. Also preferably, thebinocular further includes a flange portion that is provided to aneyepiece frame to act as a stopper for the eye cup.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a binocular according to theinvention;

FIG. 2 shows a perspective exploded view of the binocular;

FIG. 3 shows a sectional view of the binocular;

FIG. 4 shows a cross-section of the binocular;

FIG. 5 shows a perspective exploded view of a rear unit;

FIG. 6 shows a perspective view of a cam ring;

FIGS. 7A and 7B show two views of a guide ring;

FIG. 8 shows an exploded perspective view of the cam rings, the guiderings, first lens frames, and second lens frames;

FIGS. 9A and 9B show two perspective views of the rear unit;

FIGS. 10A and 10B shows two views of a belt;

FIG. 11 shows a front view of the belt and rear barrels;

FIG. 12 shows a front view of the belt and rear barrels in a differentposition from that in FIG. 11;

FIG. 13 shows an exploded perspective view of a support frame;

FIG. 14 shows a partially broken away plan view of the binocular;

FIG. 15 shows an exploded view of a focus activator and a secondactuator;

FIG. 16 shows a sectional view taken on line XVI--XVI in FIG. 14;

FIGS. 17A and 17B show two views of a cam groove;

FIGS. 18A and 18B show two views of a rear barrel;

FIG. 19 shows a cross-section of the rear portion of the rear barrel;

FIG. 20 shows a perspective view of an eye cup;

FIGS. 21A and 21B show two views of the rear portion of the rear barrel;

FIG. 22 shows a plan view of the eye cup;

FIG. 23 shows a cross-section of an eyepiece rubber;

FIGS. 24A and 24B show two views of an alternative arrangement for theeye cup; and

FIG. 25 shows a plan view of the eye cup and the rear portion of therear barrel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a perspective view of a binocular 10 according to theinvention. The binocular 10 includes parallel right and left telescopesystems 10L, 10R and a front frame 20.

In general, the telescope systems 10L, 10R in the embodiment aresymmetrical with each other. As such, wherever possible, the descriptionwill deal with the left telescope system 10L and the correspondingreference numbers for the right telescope system 10R will be shown inbrackets. Further, the term "lens" or "lenses" is used but there aremany alternative arrangements wherein these terms could be replaced by"lens group" or "lens groups" respectively.

FIG. 2 is a perspective exploded view of the binocular 10 shown in FIG.1.

As shown in FIG. 2, the telescope system 10L (10R) includes a frontbarrel 13 (14), an intermediate barrel 15 (16) and a rear barrel 31(32).

The front barrel 13 (14) fits into a bore 201 (202) formed in the frontframe 20, and is rotatably supported therein.

The intermediate barrel 15 (16) houses an erecting system (describedlater) and is fixed to the rear of the front barrel 13 (14).

The rear barrel 31 (32) is provided at the rear side of the intermediatebarrel 15 (16). The rear barrel 31 (32) is on a different optical axis(eyepiece optical axis) from the optical axis of the front barrel 13(14) (object optical axis). The intermediate barrel 15 (16) is on boththe eyepiece optical axis and the object optical axis. Parts of thebinocular 10 that are on the eyepiece optical axis comprise a rearportion of the binocular 10 and parts of the binocular 10 that are onthe object optical axis comprise a front portion of the binocular 10. Asupport frame 25 swingably supports the rear barrels 31 and 32. Theinterpupillary distance of the binocular 10 can be adjusted by swingingthe rear barrels 31 and 32.

As shown in FIG. 2, the front frame 20, the front barrels 13 and 14, andthe intermediate barrels 15 and 16 comprise a front unit 200. The rearbarrels 31 and 32 and the support frame 25 comprise a rear unit 100. Thebinocular 10 is assembled by attaching the rear unit 100 with the frontunit 200.

In order to allow easy assembly, the front barrel 13 (14) is formed witha shoulder 133 (143) which abuts an inner shoulder provided in the bore201 (202) to determine the position along the object optical axis of thefront barrel 13 (14) in the front frame 20.

The rear barrel 31 (32) has a reference surface 31a (32a) that abuts arear end surface 15a (16a) of the intermediate frame 15 (16) todetermine the position along the eyepiece optical axes of the rearbarrel 31 (32) with respect to the intermediate barrel 15 (16).

Positioning pins 31b (32b) are provided on the reference surface 31a(32a), which fit to holes 15b (16b) formed on the rear end surface 15a(16a) of the intermediate frame 15 (16) to determine the orientation ofthe rear barrel 31 (32) with respect to the intermediate barrel 15 (16)in a plane perpendicular to the eyepiece optical axis.

Further, a guide bar 311 (312) is formed on the rear barrel 31 (32)extending toward the front frame 20. On coupling the rear unit 100 tothe front unit 200, the guide bars 311 and 312 respectively fit intoguide holes 153 and 163 formed on the rear side of the intermediatebarrels 15 and 16.

FIG. 3 is a sectional view of the binocular 10. As shown in FIG. 3, thefront barrel 13 (14) houses a first lens 132 (142). The first lens 132(142) is supported by an object frame 131 (141), and the object frame131 (141) is movable along the object optical axis within the frontbarrel 13 (14).

Two Porro prisms 151, 152 (161, 162) are provided in the intermediatebarrel 15 (16). The Porro prisms 151, 152 (161, 162) constitute anerecting system.

The rear barrel 31 (32) houses a lens group that is designated as amagnifying-power-varying lens group 17a (18a). Themagnifying-power-varying lens group 17a (18a) includes a firstmagnifying-power-varying lens 112 (122) and a secondmagnifying-power-varying lens 113 (123). The first and secondmagnifying-power-varying lenses 112, 113 (122, 123) are respectivelyheld by the first and second lens frames 81, 91 (82, 92), and both firstand second lens frames 81, 91 (82, 92) are supported by the rear barrel31 (32) and are movable along the eyepiece optical axis.

An eyepiece frame 35 (36) is fixed at the rear end of the rear barrel 31(32) and supports a second lens 114 (124).

The first lens 132 (142) and the first magnifying-power-varying lens 112(122) constitute an object optical system and the secondmagnifying-power-varying lens 113 (123) and the second lens 114 (124)constitute an eyepiece optical system. A field stop 17b (18b) isprovided to the second lens frame 91 (92) at the position where an imageis formed by the object optical system.

FIG. 4 is a cross section of the telescope system 10L (10R) showing thepositions of the first and second magnifying-power-varying lenses 112,113 (122, 123) at maximum magnification (tele) and minimum magnification(wide). The positions of the first and second magnifying-power-varyinglenses 112, 113 (122, 123) at the tele position are shown above thedotted line and at the wide position are shown below the eyepieceoptical axis center line.

FIG. 5 is a perspective exploded view of the rear unit 100. The rearbarrel 31 (32) has a rotation shaft 321 (322) for connection to thesupport frame 25. The rotation shaft 321 (322) is coaxial with theobject optical axis. The rotation shaft 321 (322) is inserted through athrough-hole 251 (252) provided in the support frame 25. The rotationshaft 321 (322) has an internal thread 321a (322a) at its rear portionto which a bolt 321b (322b) is screwed.

The length of the rotation shaft 321 (322) is such that the rear barrel31 (32) is loosely supported in the axial direction by the support frame25. Therefore, when coupling the rear unit 100 to the front unit 200(FIG. 2), even if there is a difference in the axial positions of theleft and right front barrels 13 and 14 (FIG. 2), the positions along theoptical axes of the rear barrels 31 and 32 are adjustable so that theycan be aligned with respect to the intermediate barrels 15 and 16, andtherefore, with respect to the front barrels 13 and 14 (FIG. 2). Thisallows adjustment of the rear barrels 31 and 32 to ensure that thedistance between the left first lens 132 and the leftmagnifying-power-varying lens group 17a (FIG. 3) is the same as thedistance between the right first lens 142 and the rightmagnifying-power-varying lens group 18a (FIG. 3).

The rear unit 100 and the front unit 200 are first assembled and thenthe binocular 10 is assembled by coupling the rear unit 100 to the frontunit 200 as shown in FIG. 2. As such, the assembly is modular andsimple.

The rear barrel 31 also houses a driving member, for example, includinga cam ring 61 (62) and a guide ring 71 (72), for moving themagnifying-power-varying lens group 17a (18a) (FIG. 3).

The guide ring 71 (72) is provided inside the cam ring 61 (62), forlinearly guiding the magnifying-power-varying lens group 17a (18a) (FIG.3).

FIG. 6 is a perspective view of the cam ring 61 (62). As shown in FIG.6, the cam ring 61 (62) includes a cylinder portion 612 (622), an arcwall 617 (627) extending from one end of the cylinder portion 612 (622),and an extended arc wall 611 (621) extending from the end opposite thecylinder portion of the arc wall 617 (627). The arc wall 617 (627) andthe extended arc wall 611 (621) form an arc along the end of the camring 61 (62) and a remaining surface of the end of the cylinder portion612 (622) defines a reference surface 618 (628). The outer radius of theextended arc wall 611 (621) is less than the outer radius of the arcwall 617 (627) creating a shoulder surface 617a (627a). A first camgroove 613 (623) is formed on the extended arc wall 611 (621) whichallows a predetermined amount of movement of the firstmagnifying-power-varying lens 112 (122). The arc formed by the arc wall617 (627) and the extended arc wall 611 (621) around the end of thecylinder portion 612 (622) is sufficient to accommodate the first camgroove 613 (623).

A predetermined length of the cylinder portion 612 (622), measured fromthe reference surface 618 (628), is a mounting portion 619 (629) for aconnecting member (described below). The mounting portion 619 (629) hasa smaller diameter than the remainder of the cylinder portion 612 (622),providing a clearance C (FIG. 3) between the mounting portion 619 (629)and the inner surface of the rear barrel 31 (32) (FIG. 3). Two parallelslots 615, 616 (625, 626) are axially formed at a predetermined locationon the mounting portion 619 (629) and extend along the arc wall 617(627), for attaching the connecting member (described below).

Second cam grooves 614 (624) are formed on opposite sides of thecylinder portion 612 (622) to drive the second magnification powervarying lens 122 (123).

FIGS. 7A and 7B are respectively, a perspective view and a cross sectionof the guide ring 71 (72).

The guide ring 71 (72) includes a large cylinder portion 712 (722) and asmall arc wall 711 (721) that extends coaxially from an end of the largecylinder portion 712 (722). A flange portion 715 (725) is formed on theexterior of the remaining end of the large cylinder portion 712 (722).The flange portion 715 (725) includes sector gears 716 (726) in apredetermined position to be used to adjust the position of the guidering 71 (72) as described below.

Three linear guide grooves 717 (727) are axially formed on the innersurface of the small arc wall 711 (721) at intervals of 90 degrees. Anelongated hole 713 (723) is axially formed in one of the linear guidegrooves 717 (727) extending almost the entire length of the groove 717(727) and being sufficiently long to match the cam groove 613 (623) ofthe cam ring 61 (62). The arc wall 711 (721) is formed such that itforms an arc around the end of the cylinder portion 712 (722) sufficientto provide three linear guide grooves 717 (727).

Four guide groves 718 (728) are axially formed on the inner surface ofthe large cylinder portion 712 (722) at intervals of 90 degrees. Twoelongated holes 714 (724) are axially formed in two opposing guidegrooves 718 (728). The two elongated holes 714 (724) are formed to matchthe second cam grooves 614 (624) on the cam ring 61 (62).

FIG. 8 is an exploded perspective view of the cam rings 61 and 62, theguide rings 71 and 72, the first lens frames 81 and 82, and the secondlens frames 91 and 92.

The first lens frame 81 (82) has four sliders 811 (821) at intervals of90 degrees on the circumference thereof. A screw hole 812 (822) isprovided at the longitudinal center of each slider 811 (821). A cam pin813 (823) is screwed into one of the four screw holes 812 (822),selected as described below.

The first lens frame 81 (82) is supported by the guide ring 71 (72) andthe cam ring 61 (62) such that the sliders 811 (821) slidably engage thelinear guide grooves 717 (727) (FIG. 7A) of the guide ring 71 (72) andthat the cam pin 813 (823) extends through the elongated hole 713 (723)(FIG. 7A) of the guide ring 71 (72) and engages the cam groove 614 (624)of the cam ring 61 (62).

The second lens frame 91 (92) has four sliders 911 (921) formed atintervals of 90 degrees on the outer circumference thereof. A screw hole912 (922) is provided at the longitudinal center of each slider 911(921). Two cam pins 913 (923) are screwed into two of the four screwholes 912 (922) of the sliders 911 (921), selected as described below.

The second lens frame 91 (92) is supported by the guide ring 71 (72) andthe cam ring 61 (62) such that the sliders 911 (921) slidably engage thelinear guide grooves 718 (728) (FIG. 7A) of the guide ring 71 (72) andthat the cam pins 913 (923) extend through the elongated holes 714 (724)(FIG. 7A) of the guide ring 71 (72) and engage the cam grooves 614 (624)of the cam ring 61 (62).

Thus, the cam pin 813 (823) contacts the cam groove 613 (623) and thesliders 811 (821) contact the linear guide grooves 717 (727) to controlthe movement of the first lens frame 81 (82) and, at the same time, thecam pin 913 (923) contacts the cam groove 614 (624) and the sliders 911(921) contact the linear guide grooves 718 (728) to control the movementof the second lens frame 91 (92).

Since the linear guide grooves 717 (727) and the sliders 811 (821) areprovided at the same intervals, and each slider 811 (821) has a screwhole 812 (822), the cam pin 813 (823) can be fixed to any of the sliders811 (821) and that slider 811 (823) is then engaged to the guide groove717 (727) (FIG. 7A) having the elongated hole 713 (723). That is, theorientation of the first lens frame 81 (82) about the eyepiece opticalaxis can be selected. Similarly, the orientation of the second lensframe 91 (92) about the eyepiece optical axis can be selected.

The ability to select from a number of orientations about the eyepieceoptical axis is important because, in general, a lens is minutelyinclined with respect to its lens frame. In the present embodiment, anyinclination of the first magnifying-power-varying lens 112 (122) and thesecond magnifying-power-varying lens 113 (123) can be compensated for bychanging the orientation of the first lens frame 81 (82) and the secondlens frame 91 (92).

In other words, as constructed above, if there are any differencesbetween the visual field seen through the left and right telescopesystems 10L and 10R (FIG. 2) because of this minute mounting error orthe like, the visual field can be adjusted by changing the orientationof the first lens frame 81 (82) or the second lens frame 91 (92).

FIGS. 9A and 9B are perspective views of the rear unit 100, showing theoperation of a magnifying-power-varying mechanism. Themagnifying-power-varying mechanism includes the support frame 25, aconnecting member, such as a belt 40, a magnifying-power-varying knob50, a connector 53, the cam rings 61 and 62, and the guide rings 71 and72.

The belt 40 is made of a material, such as metal, which is sufficientlyrigid to transmit a rotational force to the cam rings 61, 62 andsufficiently flexible to be bent around the cam rings 61, 62 (FIG. 9).In the embodiment, the belt 40 is made of Ni--Cr--Mo alloy, for example,Hastelloy C-22 (trade mark) manufactured by Mitsubishi MaterialKabushiki Kaisha.

FIGS. 10A and 10B are respectively a front view of the belt 40 and anenlarged view of the ends of the belt 40. As shown in FIG. 10A, apredetermined length from each end of the belt 40 is bent with acurvature of radius R1, so that the curved portions 40a can be woundaround the mounting portions 619 and 629 of the cam rings 61 and 62(FIG. 9A).

As shown in FIG. 10B, a small piece at each end of the belt is bentinwardly to form bent portions 41a and 41b. Tongue portions 42a and 42bare also provided at a predetermined distance from the bent portions 41aand 41b. The tongue portions 42a and 42b are formed by cutting the belt40 and folding inwardly so that the tongue portions 42a and 42b areparallel to the bent portions 41a and 41b.

As shown in FIG. 10A, a connecting portion 43 is provided at the centerof the belt 40, for connecting the belt 40 to a connector 53 (FIG. 9)which is then connected to the magnifying-power-varying operation knob50 (FIG. 9).

As shown in FIG. 9A, the belt 40 connects the left and right cam rings61, 62, in order to synchronize the movement of the cam rings 61, 62.The belt 40 is bent around the mounting portion 619 (629) (FIG. 6) ofthe cam ring 61 (62).

FIG. 11 is a front view of the belt 40 as installed in the rear barrels31 and 32. The support frame 25 and the guide rings 71 and 72 areomitted in FIG. 11. The bent portion 41a and the tongue portion 42a ofthe belt 40 are engaged with the slots 615 and 616 of the left cam ring61. The bent portion 41b and the tongue portion 42b are engaged with theslots 625 and 626 of the right cam ring 62.

The curved portions 40a of the belt 40 wrap around the mounting portions619 and 629 and are designed to fit in clearance C (FIG. 3) between theouter surfaces of the mounting portions 619 and 629 and the innersurfaces of the rear barrels 31 and 32.

The rear barrel 31 (32) includes rollers 313 (323) along the path of thebelt 40, for guiding the belt 40. Also, support roller pair 314 (324) isprovided to the rear barrel 31 (32), for holding the belt 40therebetween, and is positioned so that a center 314a (324a) of supportroller pair 314 (324) is coaxial with the rotation shaft 321 (322) (FIG.5). Adjacent to the support roller pair 314 (324), a holding roller pair315 (325) is provided for holding the belt 40.

FIG. 12 is a front view of the belt 40, showing the status when the rearbarrels 31 and 32 are rotated from the position in FIG. 11 to adjust theinterpupillary distance. In this case, the belt 40 is supported by thesupport roller pair 314 (324) at the rotation axis so that the distancebetween the bent portion 41a (41b) and the center 314a (324a) of thesupport roller pair 314 (324) remains the same. That is, the belt 40 isnot moved longitudinally, and as such, the magnifying-power is notaffected by the adjustment of the rear barrels 31 and 32.

The gap between the guiding roller pair 314 (324) and the holding rollerpair 315 (325) is set to receive any slack in the belt 40 by allowingthe belt 40 to bend smoothly in this gap.

As shown in FIG. 10B, the outer surfaces of the bent portions 41a, 41bare curved, enabling smooth movement of the belt 40 through theclearance C (FIG. 11) without binding.

The bent portion 41a (41b) and the tongue portion 42a (42b) of the belt40 grip the slots 615 (625) and 616 (626) of the cam ring 61 (62)because the distance between the bent portion 41a (41b) and the tongueportion 42a (42b) is shorter than the distance between the slots 615(625) and 616 (626). In this way, the belt 40 is securely fastened tothe cam ring 61 (62).

As shown in FIG. 6 and FIG. 11, the slots 615, 616 (625, 626) of the camring 61 (62) extend axially and have openings 615a, 616a (625a, 626a) atthe shoulder portion 617a (627a), so that the bent portion 41a (41b) andthe tongue portion 42a (42b) of the belt 40 can be easily inserted intothe slots 615, 616 (625, 626). Also, the edges of the slots 615, 616,625 and 626 at the insertion openings 615a, 616a, 625a, and 626a arerounded to allow easy insertion of the belt 40 into the slots 615, 616,625 and 626.

As shown in FIG. 11, a holding plate 33 (34) is provided in front of thereference surface 618 (628) of the cam ring 61 (62). The holding plate33 (34) is supported by a pillar 317 (327) provided on the rear barrel31 (32). As shown in FIG. 5, on assembling the binocular, the cam ring61 (62) is pushed from the rear side by the eyepiece frame 35 (36)(described later) until the reference surface 618 (628) of the cam ring61 (62) abuts the holding plate 33 (34) so that the cam ring 61 (62) isaxially positioned.

As shown in FIG. 6, the axial length T of each of the mounting portions619 and 629 (not shown) is longer than the width of the belt 40 by apredetermined amount. Accordingly, even if there is a difference in theaxial positions of the right and left rear barrels 31 and 32, the belt40 remains substantially perpendicular to the rotation axes of the camrings 61 and 62. Therefore, the belt 40 remains substantially flat andthere is little chance of binding of the belt 40 within clearance C.

As shown in FIGS. 9A and 9B, the connector 53 is slidably provided inthe support frame 25, for transmitting the rotation of themagnifying-power-varying operation knob 50 to move the belt 40perpendicular to the eyepiece optical axes. The connector 53 isconnected to the connecting portion 43 of the belt 40. The support frame25 includes a rail 55 for guiding the movement of the connector 53.

FIG. 13 is an exploded perspective view of the support frame 25. Themagnifying-power-varying operation knob 50 is rotatably mounted to acylindrical portion 50a formed on the support frame 25. Themagnifying-power-varying operation knob 50 includes an arm 51 extendingdownward and the arm includes a pin 52. The connector 53 has a groove54, which engages the pin 52. The support frame 25 further includes afront guide bar 56, which, together with the rail 55, guides themovement of the connector 53.

By rotating the magnifying-power-varying operation knob 50, the belt 40is moved perpendicular to the eyepiece optical axes by the engagement ofthe pin 52 and the groove 54, so that the cam rings 61 and 62 (FIG. 9)are rotated.

Thus, as constructed above, the left and right magnifying-power-varyinglens groups 17a and 18a (FIG. 3) are synchronized by a simple mechanism.Further, since the dimension of the belt along the optical axis issmall, the binocular can be axially compact.

A focusing adjusting mechanism and a diopter correction mechanism arenow described with reference to FIG. 1, FIG. 14, and FIG. 15.

As shown in FIG. 1, a focus adjusting knob 183, themagnifying-power-varying operation knob 50, and a diopter correctionknob 184 are coaxially arranged at the center of the optical axes of thebinocular 10.

FIG. 14 is a plan view of the binocular 10, partially broken away. FIG.15 is an exploded view of a first actuator 181 and a second actuator182.

As is shown in FIG. 14 and FIG. 15, the first actuator 181 is providedfor transmitting the rotation of the focus adjusting knob 183 to createthe axial movement of object frames 131 and 141. The second actuator 182is provided, passing through an internal hole axially formed in thefirst actuator 181, for transmitting the rotation of the dioptercorrection knob 184 to create the axial movement of the right objectframe 141 relative to the left object frame 131.

The first actuator 181 includes a threaded portion 181a, which engageswith an internal thread 183a provided to the focus adjusting knob 183,and a head portion 181b that includes a left arm 185 for engaging theleft object frame 131, and a center bar 191 axially extending towardsthe front of the binocular 10. The arm 185 includes a slider 197 forguiding the movement of the arm 185.

The second actuator 182 includes a rod 182a and a head part 182c. Therod 182a includes an external thread 182b which engages with an internalthread 182d of the head part 182c. The head part 182c also includes aright arm 186 for engaging the right object frame 141. The right arm 186has a slider 198 for guiding the movement of the right arm 186.

FIG. 16 is a sectional view taken on line XVI--XVI in FIG. 14. Thecenter bar 191 of the first actuator 181 is guided by a center rail 192formed on the front frame 20. The sliders 197 and 198 of the left andright arms 185 and 186 are respectively guided by a pair of rails 195and 196 axially formed on the front frame 20.

Further, the left arm 185 has a rail 185a by which the right arm 186 isaxially guided and the right arm 186 is axially movable with respectiveto the left arm 185.

The left and right arms 185 and 186 are respectively held in place fromabove by regulating members 193 and 194 provided to the upper cover 180.As shown in FIG. 16, two springs 190 are respectively provided betweenthe left and right arm 185 and 186 for forcing the object frames 131 and141 downward in order to regulate the vertical position of the objectframes 131 and 141.

Further, as shown in FIG. 15, a rear shaft 187 is provided at the rearside of the first actuator 181, for rotating the second actuator 182(FIG. 14). The rear shaft 187 includes a spline 187a and a shaft portion187b. The spline 187a engages an internal spline 182e formed in thesecond actuator 182.

Rotating the focus adjusting knob 183 axially moves the first actuator181 by the engagement of the internal screw 183a and the threadedportion 181a, which then axially moves the right and left object frames131 and 141.

Rotating the diopter correction knob 184 (FIG. 13) rotates the screwportion 182b of the second actuator 182, which then axially moves thehead portion 182c thereby axially moving the right object frame 141 withrespect to the left object frame 131.

The diopter correction knob 184 is designed to be stored in a retractedposition when not in use. As shown in FIG. 13, the shaft portion 187b ofthe rear shaft 187 is supported by a cap member 184b so that the rearshaft 187 is axially movable but not rotatable with respect to the capmember 184b. The shaft portion 187b includes a flat portion which has acam groove 188 formed thereon. A spring 189 is provided to the capmember 184b. One end of the spring 189 is fixed to the cap member 184band the other end of the spring 189 is set into the cam groove 188.

FIG. 17A and FIG. 17B are, respectively, a plan view and a diagrammaticview showing the cam groove 188. The cam groove 188 is shaped as a path,proceeding from a holding portion 188a through a rising portion 188b,across a flat portion 188c, down a ledge (vertical drop) between flatportion 188c and a next flat portion 188d, turning through apredetermined angle in flat portions 188c and 188d and down anotherledge between portion 188d and holding recess portion 188e. The pathreturns from the holding recess portion 188e by first proceeding downyet another ledge between the holding recess portion 188e and areversing portion 188f in which the path turns through a predeterminedangle, then proceeding along rising return portion 188g, and finallydown another ledge between the return portion 188g and the holdingportion 188a. Thus, the path is shaped to allow the operation describedbelow.

In operation, starting from the operating position (in use position),the diopter correction knob 184 is pressed in (that is, toward the frontof the binocular 10) against the bias of the return spring 191, the tipof the spring member 189 follows the cam groove 188, and passes over thefirst two ledges along the path (creating a clicking sound), and then isreleased at the limit of movement, thus settling in the holding recessportion 188e. The diopter correction knob 184 is then held stable in aretracted position by the engagement of the tip of the spring 189 withthe cam groove 188 at the holding recess portion 188e.

The diopter correction knob 184 is then extended by pressing in againagainst the bias of the return spring 191. The tip of the spring 189follows the cam groove 188, and passes over the ledges alone, the returnpath, before settling in the holding portion 188a, at which point thediopter correction knob 184 is released. The diopter correction knob 184is then held stable in the extended position by the engagement of thetip of the spring 189 with the cam groove 188 at the holding portion188a.

In this way, the diopter correction knob 184 can be stored in themagnifying-power-varying operation knob 50 when not in use.

A fine adjustment mechanism is provided to the rear barrel 31 (32), forfine adjustment of the rotational position of the cam ring 61 (62).

FIGS. 18A and 18B respectively show perspective views of the rear barrel31 (32) with and without the guide ring 71 (72) inserted. Also referringto FIG. 8, the guide ring 71 (72) has a flange portion 715 (725) at itsrear end, which abuts the rear end of the cam ring 61 (62). The flangeportion 715 (725) has two sector gears 716 (726) for adjusting therotational position of the guide ring 71 (72).

As shown in FIG. 18B, two recesses 314 (324) are formed on the innersurface of the rear barrel 31 (32). As shown in FIG. 18A, the sectorgears 716 (726) of the guide ring 71 (72) fit to the recesses 314 (324)of the rear barrel 31 (32). An adjusting margin M is provided betweenthe recesses 314 (324) and the sector gears 716 (726), to allow thesector gears 716 (726) to be rotated for fine adjustment of therotational position of the guide ring 71 (72). The rear barrel 31 (32)has an opening 315 (325), for operating one of the sector gears 716(726).

FIG. 19 is a cross section of the rear portion of the rear barrel 31(32). As shown in FIG. 19, the opening 315 (325) is covered by an eyecup 37 having an opening 378 corresponding to the opening 315 (325). Theopening 378 is covered by a rubber cover 39, which prevents unintendedoperation of the fine adjustment mechanism.

The sector gear 716 (726) is easily operated by removing the rubbercover 39, even after the binocular 10 is assembled.

As shown in FIG. 8, when the guide ring 71 (72) is rotated by theoperation of the sector gear 716 (726), the guide ring 71 (72) minutelyrotates with reference to the cam ring 61 (62). Accordingly, the guidegrooves 713 (723) and 718 (728) (FIG. 7A) shift with reference to thecam groove 614 (624) (FIG. 6). Thus, the axial moving range of the lensgroup 17a (18a) with reference to the rotation of the cam ring 61 (62)can be changed.

Accordingly, the axial movement range of the left and rightmagnifying-power-varying lens groups 17a and 18a can be adjustedseparately.

As shown in FIG. 19, the eyepiece frame 35 (36) is provided to the rearbarrel 31 (32), for holding the second lens 114 (124) (FIG. 3). Theeyepiece frame 35 (36) is mounted to the rear barrel 31 (32), byengaging a threaded portion 351 (361) of the eyepiece frame 35 (36) toan internal thread 316 (326) formed in the rear barrel 31 (32).

The position of the cam ring 61 (62) and the guide ring 71 (72) areaxially fixed by mounting the eyepiece frame 35 (36) to the rear barrel31 (32).

FIG. 20 is a perspective view of the eye cup 37. The eye cup isidentical for both telescope systems and the right rear barrel 32 is notshown. The eye cup 37 is mounted from the rear side of the rear barrel31 before the eyepiece frame 35 is mounted. The eyepiece frame 35 has aflange portion 353 which has a diameter that is slightly larger thanthat of the rear barrel 31, and the flange portion 353 acts to securethe eye cup 37.

FIGS. 21A and 21B are respectively a cross section of the rear portionof the rear barrel 31. Two rectangular protrusions 371 and 372 areformed on the eye cup 37, and three rectangular indentations 321, 323and 325 are formed on the rear barrel 31, so that the two rectangularprotrusions 371 and 372 can selectively fit in two of the threerectangular indentations 321, 323 and 325. The protrusions 371 and 372and the indentations 321, 323 and 325 are rectangle shaped.

FIG. 22 is a plan view of the eye cup 37. The indentations 321, 323 and325 are formed in a groove 322 having the same width as the indentations321, 323 and 325, which is the same as the width of the protrusions 371and 372.

When the protrusions 371 and 372 engage the indentations 321 and 323,the eye cup 37 projects from the rear barrel 31 as shown in FIG. 21B,and when the protrusions 371 and 372 engage the indentations 323 and325, the eye cup is stored as shown in FIG. 21A. As constructed above,the eye cup 37 can be securely held in either position.

As shown in FIG. 21A, an eyepiece surface 352 of the eyepiece frame 35is shaped with a curvature radius R2 in order to avoid interferencebetween the eyepiece surface 352 and a user's spectacles. The curvatureradius R2 is a predetermined value that is based on a typical curvatureradius of spectacle lenses. In the embodiment, the curvature radius R2is set to 100 mm.

As shown in FIG. 21A, the eyepiece rubber 39 is mounted to the eye cup37. FIG. 23 is a cross section of the eyepiece rubber 39. As shown inFIG. 23, the surface 392 of the eyepiece rubber 39 has a curvatureradius R3 with a center of curvature X that is positioned at a distanceS from the optical axis O. This offset curvature radius R3 allows theeyepiece rubber 39 to shield the user's eye from ambient light.

Although the structure and operation of a binocular is described hereinwith respect to the preferred embodiments, many modifications andchanges can be made without departing from the spirit and scope of theinvention.

FIGS. 24A and 24B show an alternative arrangement of the left rearbarrel 31 (similar for the right rear barrel 32) and the eye cup 37. Inthis arrangement, three openings 361, 362 and 363 are formed on the eyecup 37, and two protrusions 341 and 342 are formed on the rear barrel31, such that the two protrusions 341 and 342 can selectively fit intotwo of the three openings 361, 362 and 363.

FIG. 25 is a plan view of an eye cup 37 and the rear portion of the rearbarrel 31. The protrusions 341 and 342 and the three openings 361, 362and 363 are rectangular shaped. The three openings 361, 362 and 363 areformed in a groove 360 having the same width as the openings 361, 362and 363 and also the same as the width of the protrusions 341 and 342.

When the protrusions 341 and 342 respectively engage openings 361 and362, the eye cup projects from the rear barrel 31 as shown in FIG. 24B,and when the protrusions 341 and 342 engage the openings 362 and 363,the eye cup is stored as shown in FIG. 24A. As such, the eye cup 37 canbe securely held in either position.

The present disclosure relates to subject matter contained in JapanesePatent Application Nos. HEI 07-239091, HEI 07-239297, HEI 07-239298, HEI07-239299, HEI 07-239300, HEI 07-239301, HEI 07-239302, HEI 07-239303,HEI 07-239304, HEI 07-239305, and HEI 07-239306 filed on Aug. 24, 1995,which are expressly incorporated herein by reference in their entirety.

What is claimed is:
 1. A binocular comprising:two telescope systemshaving parallel optical systems, each telescope system including amagnifying-power-varying lens group; a magnifying-power-varyingmechanism that moves said magnifying-power-varying lens groups, saidmagnifying-power-varying mechanism comprising drive members that arerotatably provided to axially move said magnifying-power-varying lensgroups and a connecting member that connects said drive members, whereinsaid connecting member is provided to synchronously rotate said drivemembers, said connecting member comprising a belt-shaped member havingdiscrete longitudinal ends and having a predetermined rigidity, saidconnecting member comprising an engaging portion at both longitudinalends to be engaged with said drive members, each of said engagingportions comprising a bent portion at the longitudinal end of saidconnecting member and a tongue portion formed at a predetermineddistance from said end portion, and said longitudinal ends of saidbelt-shaped member being fixed to outer surfaces of said drive members,predetermined lengths of said belt-shaped member, extending from saidlongitudinal ends, having a bend of a predetermined curvature, whereinwhen said connecting member is driven perpendicular to said opticalaxes, said connecting member pushes the outer surface of one of saiddrive members and pulls the outer surface of the other of said drivemembers thereby rotating both of said drive members.
 2. The binocularaccording to claim 1, wherein a portion adjacent each of said bentportions has a bend of a predetermined radius.
 3. The binocularaccording to claim 1, wherein said connecting member is made of metal.4. The binocular according to claim 3, wherein said connecting member ismade of a Ni--Cr--Mo alloy.
 5. The binocular according to claim 1,further comprising a guiding mechanism that guides said belt-shapedmember, said guiding mechanism comprising a plurality of rollerssupporting said belt-shaped member.
 6. A binocular comprising:twotelescope systems having parallel optical systems, each telescope systemincluding a magnifying-power-varying lens group; and amagnifying-power-varying mechanism that moves saidmagnifying-power-varying lens groups, comprising drive members thataxially move said magnifying-power-varying lens groups and a connectingmember that connects said drive members, said connecting membercomprising a belt-shaped member having discrete longitudinal ends, atleast a portion of said belt-shaped member being flexible; and whereinsaid belt-shaped member has bent portions at both said longitudinal endsand tongue portions formed at a predetermined distance from said bentportions, wherein said drive members have slots for engaging each ofsaid bent portions and each of said tongue portions.
 7. The binocularaccording to claim 6, wherein each of said tongue portions comprises arectangularly-shaped portion extending from said connecting member,having been cut and bent therefrom.
 8. The binocular according to claim7, wherein the distance between each said bent portion and each saidtongue portion is less than the distance between said slots of eachdrive member, so that said bent portion and said tongue portion clampsaid connecting member to said drive members.
 9. The binocular accordingto claim 7, wherein a predetermined length from both longitudinal endsof said connecting member are wound around said drive members.
 10. Thebinocular according to claim 9, wherein said slots of each drive memberhave openings at one longitudinal end surface of said drive member, forreceiving said bent portion and said tongue portion.
 11. The binocularaccording to claim 10, wherein said slots are flared at said opening forinserting said bent portion and said tongue portion.
 12. The binocularaccording to claim 6, a distance between said bent portion and saidtongue portion of each longitudinal end of said belt-shaped member beingsmaller than a distance between said slots of each of said drivemembers.
 13. The binocular according to claim 6, further comprising aguiding mechanism that guides said belt-shaped member, said guidingmechanism comprising a plurality of rollers supporting said belt-shapedmember.
 14. A binocular comprising:two telescope systems having paralleloptical systems, each telescope system including amagnifying-power-varying lens group; and a magnifying-power-varyingmechanism that moves said magnifying-power-varying lens groups, saidmagnifying-power-varying mechanism comprising drive members, aconnecting member and a regulating member, said drive members comprisingdrive rings rotatably provided for axially moving saidmagnifying-power-varying lens groups, said connecting member comprisinga belt-shaped member having discrete longitudinal ends and apredetermined rigidity and that synchronously rotates said drive rings,said regulating member regulates the position of said connecting memberin a predetermined direction parallel to the optical axes of saidmagnifying-power-varying lens groups, said regulating member comprises aregulating plate provided in front of said connecting member; and saiddrive rings have reference surfaces, and said regulating plate contactssaid reference surfaces to thereby regulate said drive rings in saidpredetermined direction.
 15. The binocular according to claim 14,wherein said regulating plate elasticly regulates the movement of saiddrive rings.
 16. The binocular according to claim 14, further comprisinga guiding mechanism that guides said belt-shaped member, said guidingmechanism comprising a plurality of rollers, said belt-shaped memberpositioned between said plurality of rollers.
 17. A binocularcomprising:two telescope systems having parallel optical systems, eachtelescope system including an objective optical system, amagnifying-power-varying lens group and an eyepiece optical system, eachsaid eyepiece optical system being rotatable about an axis of one ofsaid objective optical systems; and a magnifying-power-varying mechanismthat moves said magnifying-power-varying lens groups, saidmagnifying-power-varying mechanism comprising drive members that arerotatably provided to axially move said magnifying-power-varying lensgroups and a connecting member that connects and synchronously rotatessaid drive members, said connecting member comprising a belt-shapedmember having a predetermined rigidity, and longitudinal ends of saidbelt-shaped member being fixed to outer surfaces of said drive members,said belt-shaped member being bendable at said rotation axes of saideyepiece optical systems.
 18. The binocular according to claim 17,further comprising at least one roller that guides a movement of saidbelt-shaped member, said at least one roller being co-axial with said ofone of said objective optical systems.
 19. The binocular according toclaim 17, further comprising at least two rollers for guiding saidbelt-shaped member with respect to each of said drive members, a gapbetween said rollers of each of said pair of rollers receiving a slackof said belt-shaped member.
 20. The binocular according to claim 17,rotation of said eyepiece optical systems about said axes of saidobjective optical systems enabling for interpupillary adjustment. 21.The binocular according to claim 17, further comprising a guidingmechanism that guiding said belt-shaped member, said guiding mechanismcomprising a plurality of rollers, said belt-shaped member positionedbetween said plurality of rollers.